On 03/22/14 23:55, [email protected] wrote:
> From: Mark Charlebois <[email protected]>
>
> Replaced non-standard C use of Variable Length Arrays In Structs (VLAIS) in
> xt_repldata.h with a C99 compliant flexible array member and then calculated
> offsets to the other struct members. These other members aren't referenced by
> name in this code, however this patch maintains the same memory layout and
> padding as was previously accomplished using VLAIS.
>
> Had the original structure been ordered differently, with the entries VLA at
> the end, then it could have been a flexible member, and this patch would have
> been a lot simpler. However since the data stored in this structure is
> ultimately exported to userspace, the order of this structure can't be changed.
>
> This patch makes no attempt to change the existing behavior, merely the way in
> which the current layout is accomplished using standard C99 constructs. As such
> the code can now be compiled with either gcc or clang.
>
> This version of the patch removes the trailing alignment that the VLAIS
> structure would allocate in order to simplify the patch.
>
> Author: Mark Charlebois <[email protected]>
> Signed-off-by: Mark Charlebois <[email protected]>
> Signed-off-by: Behan Webster <[email protected]>
> Signed-off-by: VinÃcius Tinti <[email protected]>
> ---
> net/netfilter/xt_repldata.h | 22 +++++++++++++++++-----
> 1 file changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/net/netfilter/xt_repldata.h b/net/netfilter/xt_repldata.h
> index 6efe4e5..8fd3241 100644
> --- a/net/netfilter/xt_repldata.h
> +++ b/net/netfilter/xt_repldata.h
> @@ -5,23 +5,35 @@
> * they serve as the hanging-off data accessed through repl.data[].
> */
>
> +/* tbl has the following structure equivalent, but is C99 compliant:
> + * struct {
> + * struct type##_replace repl;
> + * struct type##_standard entries[nhooks];
> + * struct type##_error term;
> + * } *tbl;
> + */
> +
> #define xt_alloc_initial_table(type, typ2) ({ \
> unsigned int hook_mask = info->valid_hooks; \
> unsigned int nhooks = hweight32(hook_mask); \
> unsigned int bytes = 0, hooknum = 0, i = 0; \
> struct { \
> struct type##_replace repl; \
> - struct type##_standard entries[nhooks]; \
> - struct type##_error term; \
> - } *tbl = kzalloc(sizeof(*tbl), GFP_KERNEL); \
> + struct type##_standard entries[]; \
> + } *tbl; \
> + struct type##_error *term; \
> + size_t term_offset = (offsetof(typeof(*tbl), entries[nhooks]) + \
> + __alignof__(*term) - 1) & ~(__alignof__(*term) - 1); \
> + tbl = kzalloc(term_offset + sizeof(*term), GFP_KERNEL); \
> if (tbl == NULL) \
> return NULL; \
> + term = (struct type##_error *)&(((char *)tbl)[term_offset]); \
> strncpy(tbl->repl.name, info->name, sizeof(tbl->repl.name)); \
> - tbl->term = (struct type##_error)typ2##_ERROR_INIT; \
> + *term = (struct type##_error)typ2##_ERROR_INIT; \
> tbl->repl.valid_hooks = hook_mask; \
> tbl->repl.num_entries = nhooks + 1; \
> tbl->repl.size = nhooks * sizeof(struct type##_standard) + \
> - sizeof(struct type##_error); \
> + sizeof(struct type##_error); \
> for (; hook_mask != 0; hook_mask >>= 1, ++hooknum) { \
> if (!(hook_mask & 1)) \
> continue; \
Any further feedback about this patch?
Behan
--
Behan Webster
[email protected]